Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1998-06-29
2000-02-29
Nazario-Gonzalez, Porfirio
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
562486, 4221841, C07C 5109, C07C 5142, B09B 500
Patent
active
060311282
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a process for manufacturing terephthalic acid and more particularly, to a process of manufacturing and recovering the highly purified terephthalic acid using an alkali weight-reduction waste water discharged from weight-reduction process in a polyester textile dyeing complex, in accordance with the practice of this invention comprising the following procedures: polyethylene terephthalate (hereinafter referred to "PET") waste scrap materials are hydrolyzed to prepare the slurry of disodium terephthalate. Then, said slurry dissolved in water is adsorbed to remove impurities, and followed by acid-neutralization to obtain terephthalic add of this invention.
"Alkali weight-reduction waste water" is a remaining reactant discharged in a weight reduction-processing stage which is designed to give the polyester textile a silky property, as well as to improve the dyeing capability by treating the polyester textile with sodium hydroxide or another basic aqueous solution, and thereby causing a part of the textile to become depolymerization. Said alkali waste water is a strong alkali solution of over pH 11 with a large amount of sodium hydroxide and disodium terephthalate.
In the past, a considerable amount of alkali weight-reduction waste water, generated from the large industrial complex crowded with dyeing plants, has been directly discharged by a conventional waste water treatment. Besides that, sludges neutralized with such strong acid as hydrochloric acid or sulfuric acid have been used for landfills or sea-abandonments, while the remaining reactants have been discharged by a conventional waste water treatment. Therefore, alkali weight-reduction waste water generated from the conventional weight-reduction process for polyester textile has caused severe environmental problems and such treatment conventionally requires a large amount of investment for anti-pollution facilities.
In addition, the PET waste scrap materials, which are discharged after using them from the end-users, refer to polyester scrap textiles, PET scrap bottles, PET scrap containers, PET scrap chips generated in the polymerization process of PET, or polyester scrap yarns generated from the process of manufacturing polyester fibers, yarns and textiles. The need for the reutilization of the PET scrap, being incessantly discharged by one's daily life or in the manufacturing process, has created a great issue in the viewpoint of reducing production costs and abating environmental problems. Recently, various processes have been proposed for the recovery of terephthalic acid from the PET scrap, or polyester weight-reduction waste water but no process to manufacture and recover terephthalic acid, using both PET scrap and polyester weight-reduction waste water, has been reported up to now.
The conventional processes of manufacturing and recovering terephthalic acid are as follows, using the PET scrap:
In U.S. Pat. Nos. 3,120,561 and 4,578,502, PET was hydrolyzed at high temperature and pressure, cooled rapidly and crystallized to recover the precipitated terephthalic acid.
In U.S. Pat. No. 3,884,850, bis(hydroxyethyl) terephthalate was employed as a solvent to recover terephthalic acid from PET.
In U.K. Pat. No. 2,123,403 and Japanese Patent Unexamined Publication No. 3-16,328, PET was hydrolyzed with a solvent such as water in the presence of decoloring carbon at 200 to 300.degree. C., then cooled under reduced pressure to recover terephthalic acid.
In U.S. Pat. No. 3,952,053, two methods related the recovery of terephthalic acid from PET as follows: a) through the hydrolysis with sulfuric acid, the obtained mixing solution consisting of terephthalic acid and sulfuric acid was precipitated by water to recover terephthalic acid, or b) PET was placed in an aqueous solution of sodium hydroxide to precipitate unsoluble materials for removal and sulfuric acid was added to precipitate terephthalic acid. Then, ethylene glycol was extracted with organic solvent and distilled after
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Bae Dongmok
Roh Hang-Duk
Nazario-Gonzalez Porfirio
Sunkyong Industries Co., Ltd.
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